U.S. Pat. No. 5,411,585 discloses a method of improving the stability of aqueous media containing certain organosilanes with silicon-bonded hydrolyzable groups. As explained in U.S. Pat. No. 5,411,585 such aqueous compositions have various uses. The hydrolyzable groups enable the compounds to attach themselves to suitable surfaces. The organosilanes are not stable in aqueous media, however, and U.S. Pat. No. 5,411,585 discloses that the stability of aqueous solutions of defined organo-silanes may be improved by the addition of a) a defined water-soluble organic quaternary ammonium compound and b) certain surfactants other than the quaternary ammonium compound. The patent specification defines the organo-silane as being water-soluble at 25.degree. C. and states that organo-silanes which do not give clear solutions at 25.degree. C. are not useful.
Organo-silicon compounds are available which have low solubilities in water and which thus do not form clear solutions in water. Thus fluoro-silanes are available which are hydrolyzed by water and may be used to treat surfaces to impart desirable properties to them. The mixture of water and fluoro-silane has however a pot life of only a few hours before it becomes unusable. This makes it impossible to market a ready-mixed aqueous product which is suitable for consumer use and which has an acceptable shelf-life for retail sales.
U.S. Pat. No. 5,531,814 discloses an aqueous composition containing silicon compounds and various water-soluble solvents. The silicone compounds are siloxane compounds, i.e., they contain chains of Si--O groups. Among the solvents listed is propylene glycol n-butyl ether and dipropylene glycol n-butyl ether. There is no suggestion that the aqueous compositions have any problem with lack of stability.
It has now been found that problems with the stability of hydrolysable silicon compounds having poor solubility in water may be reduced by choice of a limited class of co-solvents.